There are injection devices from the related art in various embodiments. What is particularly important in this area is the production by the injection device of an optimum fuel-air mixture, usually referred to as a spray, for combustion in the combustion chamber. Such injection devices are, however, very complex and, in particular, expensive since to prepare the spray either high system pressures are generated in order to convert hydraulic pressure energy into kinetic energy or, in alternative methods, spray production is accomplished using high-frequency shock waves.
German patent document DE 10 2006 026 153 A1, for example, discusses spray production using high-frequency shock waves generated by piezo actuators. In that case, the actuator is situated in the medium to be injected. The shock-wave-exciting element is also situated in the medium to be injected in the case where shock waves are generated by a defined spark discharge. In that case, some of the medium to be injected is subjected in addition to extremely high temperatures. The contact of the actuators used to generate the shock waves with the medium that is to be injected may lead to interactions between the medium and the actuators, which may result in chemical or physical damage both to the medium to be injected and to the actuators. Furthermore, the quality of the spray is unsatisfactory as regards droplet size distribution and velocity of the spray front both in the case of actuators for spark discharge and in the case of piezo actuators.
For that reason, the solutions mentioned have only inadequate suitability for use in, for example, modern diesel engines.